Where can I get the first Blender 2.8 build?
the first build with EEVEE


is a rather arbitrary point in time, the blender 2.80 evee development started as a branch from the current development of blender, it was identical to the normal blender releases. There have been no tagged releases containing evee, the daily test builds have been the only available versions.

As blender is open source, you can build any variation of it that you want. The blender 2.80 development is being done in it's own branch so you just add git branch blender2.8 after you have a copy of the repo. You can list the history of the branch and checkout any commit from that list that you want and compile it as it was at that point in time.

So you can build any version that you want, but to get daily experimental pre-built binaries you have to get them the day they are available.